/*
 * The MIT License
 *
 * Copyright (c) 2009 André D. Piske
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 */
package org.gohtml;

/**
 * This is like a stack (LIFO) of chars.
 * It's designed to be faster than the {@link java.util.Stack} class.
 *
 * @since 0.1 alpha
 * @version 0.1 alpha
 * @author André D. Piske
 */
public final class Backreader {

    private char[] buffer;
    private int bufferSize, bufferPos;

    protected void assertSize(int newSize) {
        if (newSize > bufferSize) {
            if (buffer == null) {
                buffer = new char[newSize];
            } else {
                char b[] = new char[bufferSize];
                System.arraycopy(buffer, 0, b, 0, bufferSize);
                buffer = new char[newSize];
                System.arraycopy(b, 0, buffer, 0, bufferSize);
            }
            bufferSize = newSize;
        }
    }

    public Backreader() {
        bufferPos = 0;
        assertSize(1024);
    }

    public void pushString(String s) {
        int length = s.length();
        assertSize(bufferPos + length + 1024);
        for (int j = 0; j < length; ++j) {
            buffer[bufferPos + j] = s.charAt(length - (j + 1));
        }
        bufferPos += length;
    }

    public void push(char ch) {
        if (bufferPos > bufferSize) {
            assertSize(bufferPos + 1024);
        }
        buffer[bufferPos++] = ch;
    }

    public int skip(int length) {
        int pos = bufferPos;
        if (length > pos) {
            bufferPos = 0;
            return pos;
        } else {
            bufferPos -= length;
            return length;
        }
    }

    public int pop() {
        if (bufferPos == 0) {
            return -1;
        }
        return buffer[--bufferPos];
    }

    public boolean isEmpty() {
        return (bufferPos == 0);
    }
}
